The navigation of the distal end of a medical device through the body, whether by conventional mechanical means or magnetic means, is usually facilitated by x-ray imaging of the operating region. However, when there is radiopaque material in the operating region, it is often difficult to discern the distal end of the medical device. This occurs, for example when the medical device is delivering a radiopaque material, such as a radiopaque embolic material, or a radiopaque embolization coil. The presence of these materials in the medical device or in the operating region can make it difficult for the physician to “see” the distal end of the medical device on x-ray images, and thus make it difficult to quickly and accurately navigate the distal end of the medical device.